Effect of hetero-contacts at active material conductive additives on lithium intercalation/deintercalation of LiCoO2

The effect of hetero-contacts at electroactive material I conductive Additi ves on electrochemical lithium intercalation/deintercalation to LiCoO2 have been investigated by using the pure and binder-free LiCoO2 thin film elect rode and the pellet electrode of the pellet of LiCoO2 electroactive materia l powder, conductive additive and organic binder. It was found that the tra nsport rate of lithium ion inside these pellet electrodes had quite differe nt values in anodic and cathodic polarization, and it strongly depends on t he amount of conductive additive and the material itself. These behaviors c ould not be explained by the penetration of the organic electrolyte solutio n and by the concentration gradients as a driving force of lithium ion tran sport inside the LiCoO2 lattice. Carbon conductive additive drastically inc reased the rate of lithium ion transport inside the pellet electrode and Li CoO2 active material. This effect was remarkably large in cathodic polariza tion than that in anodic polarization.